In a manufacturing process of a semiconductor device, a surface of a substrate such as a semiconductor wafer is processed by using a processing liquid. A single-substrate-processing apparatus processing semiconductor wafers one by one comprises a spin chuck rotating a substrate while holding the substrate horizontally, and a nozzle for supplying the processing liquid to a surface of the substrate rotated by the spin chuck.
In a typical substrate processing step, a chemical liquid is supplied to a substrate held by a spin chuck. Thereafter, a rinsing liquid is supplied to the substrate, whereby the chemical liquid on the substrate is replaced by the rinsing liquid. Thereafter, a spin drying step for eliminating the rinsing liquid on the substrate is executed. In the spin drying step, the substrate is rotated at a high speed, whereby the rinsing liquid adhered on the substrate is flicked off and removed (dried). A usual rinsing liquid is deionized water.
When a fine pattern is formed on a surface of a substrate, there may be a problem that a rinsing liquid entering an inside of the pattern cannot be removed in a spin drying step, whereby insufficient drying may occur. Therefore, there has been proposed an approach of drying a surface of a substrate by supplying a surface of a substrate after processing by using a rinsing liquid with an organic solvent such as isopropyl alcohol (IPA) to replace a rinsing liquid entering a clearance of a pattern of the surface of the substrate with the organic solvent.
As shown in FIG. 18, in a spin drying step where a substrate is dried by rotating the substrate at a high speed, a liquid surface (boundary surface between air and a liquid) is formed in a pattern. In this case, a surface tension arises at a contact position between the liquid surface and the pattern. This surface tension is one of causes which collapse the pattern.
As described in following Patent document 1, when a liquid of an organic solvent is supplied to a surface of a substrate after a rinsing treatment and before a spin drying step, the liquid of the organic solvent enters a pattern. A surface tension of the organic solvent is lower than that of water which is a typical rinsing liquid. Therefore, a problem of a pattern collapsing due to a surface tension is relieved.
Further, a substrate processing apparatus described in Patent document 1 includes a solvent nozzle opposed to an upper surface center portion of a substrate held by a spin chuck and discharging IPA to the upper surface center portion of the substrate, and a center gas nozzle holding and encompassing the solvent nozzle and discharging inert gas above the substrate held by the spin chuck.
After the rinsing treatment, inert gas is discharged from the center gas nozzle. Thus, a gas flow of nitrogen gas flowing radially along a fluid film of pure water covering the entire upper surface of the substrate is formed. Further, in parallel with discharging of the inert gas from the center gas nozzle, IPA is discharged from the solvent nozzle toward the upper surface center portion of the substrate in a rotated state.